The currently extensive usage of small vehicles such as snowmobiles, all terrain vehicles, motorcycles, and rideable work vehicles such as lawn mowers, frequently necessitates the transportation of such vehicles to and from recreational and work locations. A problem commonly experienced relates to the safe loading and unloading of a vehicle as well as to transporting and storing of a suitable loading ramp since small trucks or trailers are frequently used and little storage space is available. As a result, makeshift loading and unloading arrangements using wood planks and the like for loading and unloading purposes may be used. Safety may then be deferred in favor of convenience which places the operator at risk together with his equipment.
A portable ramp suitable for loading and unloading small vehicles is disclosed in U.S. Pat. No. 3,984,891, issued Oct. 12, 1976 to Carl E. Weinmann. Although eminently suited to the task, the Weinmann ramp is not well adapted for convenient, compact storage. In this regard, the ramp is fabricated from a plurality of extruded members that require assembly and disassembly each time the ramp is used and then subsequently stored. Consequently, the Weinmann ramp is not well suited to domestic applications in which apparatus costs and convenience of use are principal considerations of ramp selection.
Recourse to the collapsible ladder art shows a type of construction that may be adapted to meet a portable ramp criterion of compactness. In this respect, U.S. Pat. No. 3,061,042, issued Oct. 30, 1962 to C. W. Giles together with U.S. Pat. No. 4,429,766, issued Feb. 7, 1984 to D. Salvador Alimbau Marques each show a ladder construction having a plurality of U-shaped modules that slidably nest together. Both Giles and Alimbau Marques disclose modules comprising a base and a pair of upright sections, with each module being smaller in width than the preceding module which facilitates the nesting arrangement when all of the modules are contracted. Although this nesting arrangement facilitates the ramp criteria of compactness and convenient storage, this arrangement results in an unstable ramp structure at the end where the U-shaped modules are narrow. Furthermore, a rigid sliding arrangement which is desirable in ladders and which is disclosed by Alimbau Marques is undesirable in a ramp construction which requires a pivotal quality to accommodate various differences in height between loading and unloading surfaces.